Decolorization of CI Reactive Black 8 by electrochemical process with/without ultrasonic irradiation

Abstract

Abstract The decolorization of CI Reactive Black 8 by anodic oxidation with Ti/RuO2-IrO2 anode and stainless steel cathode was carried out in an electrochemical cell with or without ultrasonic irradiation. The effect of current density, initial pH value, initial dye concentration and electrolyte concentration on the decolorization rate of CI Reactive Black 8 in both two processes was investigated. The results showed that the decolorization followed pseudo-first-order kinetics. The decolorization rate increased with increasing the current density, but decreased with increasing the initial dye concentration and electrolyte concentration. The acidic condition favored CI Reactive Black 8 decolorization. The presence of ultrasonic irradiation could enhance electrochemical oxidation (EC) of CI Reactive Black 8, and the enhancement effect tended to increase with increasing the initial dye concentration, pH value, and electrolyte concentration, but decrease with increasing the current density. In the presence of ultrasonic irradiation, a 32.4% COD removal efficiency was achieved after 90 min EC when initial concentration was 100 mg l−1, current density was 31.7 mA cm−2, initial pH value was 5.4, the electrolyte concentration was 0.1 mol l−1 and the acoustic power was 100 W l−1. The specific oxygen uptake rate (SOUR) tests showed that SOUR decreased during the first 15 min, but it increased with reaction time afterwards.